Supplementation with L-kynurenine during in vitro maturation improves bovine oocytes developmental competence through its antioxidative action.

Oxidative stress impairs the developmental potential of oocytes during in vitro maturation (IVM). L-kynurenine (L-KYN), an endogenous metabolite, exhibits antioxidant, anti-inflammatory and neuroprotective effects. This work aimed to evaluate the potential effects of L-KYN on bovine oocyte IVM and its mechanisms. Different concentrations of L-KYN (0, 10, 50, 100, and 200 μmol/L) were supplemented to bovine oocyte IVM medium. Results shown a notable enhancement in the oocyte maturation rate and the subsequent zygote cleavage and blastocyst formation rate when the L-KYN concentration reached 100 μmol/L. Further analysis revealed that this treatment effectively down-regulated expression levels of genes to cumulus cell apoptosis (Bax and Caspase3), up-regulated expression levels of genes to cumulus cell expansion (HAS2, PTX3, and PTGS2) and oocyte antioxidant (GPX4 and CAT). L-KYN supplementation also effectively increased glutathione (GSH) levels, promoted oocytes mitochondrial activity, enhanced DNA repairability, deceased reactive oxygen species (ROS) levels, and reduced apoptosis. In conclusion, adding 100 μmol/L of L-KYN to IVM medium could enhance bovine oocyte quality and the subsequent embryonic development. L-KYN could be a potential antioxidant supplement for bovine oocyte maturation in vitro.